Manufacture of ethyl benzene



Oct. 17, 1944'. w. J. MATTOX 2,360,358

MANUFACTURE OF ETHYL BENZ-ENE 'Filed Feb. 11, 1942 2 Sheets-Sheet 1 BENZENE a ETHYLENE CHARGE ALKYLATION gauzms 3 & ETHYLENE ,4 SEPARATION 6 17 4 {MONO ETHYL BENZENE I71 l5 v HYDROGEN A HALIDE x 1 4 I j Y r6 J DEALKYLATION 9 BENZENE 'PoLYETHYg, ETHYLENE/ l8 I3 BENZENE I I (I0 I T SEPARATION I9 19' I kl! HYDROGEN & TOLUENE i'ARAFFIN GAS I ATTORN-EY Oct. 17, 1944. w J MATTOX 2,360,358

' MANUFACTURE OF ETHYL BENZENE I Filed Feb. 11, 1942 2 Sheets-Sheet 2 BENZENE 8- ETHYLENE CHARGE ALKYLATI ON V 23 MONO ETHYL r 24 BENZENE BENZENE SEPARATION 31 I ETOLUENE BENZENEJ ETHYLENE- DEALKYLATION HYDROGEN I30 SEPARATION J HYDROGEN &

PARAFFIN GASES FIG. 2

l NVENTOR WILLIAM J. MATTOX Patented Oct. 17, 1944 f UNITED STATES PATIENT OFFICE MANUFACTURE OF ETHYL BENZENE V William J. Mattox, Chicago, 111., assignor to Universal Oil Products Company, Chicago; III., a

corporation of Delaware Application February 11, 194a Serial No. 430,503

2 Claims. (c1.- 260-671) i This invention relates to a process for producing monoethylbenzene from benzene and ethyle118. j

In the alkylation of benzene with ethylene to produce monoethylbenzene there is simultaneously produced relatively large quantities of polyvethylbenzenes. These products in general are less desirable and have a' lower market value than the monoethylbenzene because 01- the demand for the latter in the production of styrene which is useful as a raw material for manufacture of high molecular weight polymers and syn-- thetic' rubber. I

In one specific embodiment my invention com;v prises alkylating benzene'with ethylene, sepa rating monoethylbenzene, subjecting polyethylbenzene to a. dealkylation treatment to produce monoethylbenzene, separating and recovering the monoethylbenzene, returning a portion of unconverted polyethylbenzenes to the dealkylation treatment, and retuminga'portion oi theliquid hydrocarbons boiling below monoethylbenzene to the dealkylation step and another portion together with ethylene to the alkylation step. I

The invention may be understood by reference to the accompanying Figure 1 and Figure 2 which are diagrammatic and should not be interpreted as limiting it to the exact conditions shown therein.

Referring to Figure 1, benzene and ethylene are introduced through line to alkylation step 2.,

The alkylated products pass through line 3' to separation step 4. Monoethylbenzene is removed halide, in zone 8, the hydrogen halide is introduced through line I! to the dealkylation step.

The hydrogenhalide recovered from separation Toluene may be recovered through line 25. The, light fraction comprising mainly benzene may be removedthrough line 26 to the alkylation step.

At least a part of this fraction passes through line 21 joining with the'polyethylbenzenes in line 28 and is passed todealkylation step 29. The fraction removed through lines 26 and 21 may comprise all of thehydrocarbons boiling below monoethylbenzene. However, when substantial quantities of toluene are formedit is desirable to separately recover this valuable product. The reaction products from the dealkylation step 29 pass through line 30 to separator 3|. All of the liquid products are supplied through line 32 to through line 5. Unconverted benzene is returned to the alkylation step through line B together with reaction products hereinafter described. Polyethylbenzenes pass from separation step 4, through line I to dealkylation step 8 wherein the "polyethylbenzene is partially dealkylated to monoethylbenzene. The reaction products pass through line 9 to separation step It. Monoethylbenzene is removed through line H to storage.

. Polyethylbenzenes are recycled through line l2 to dealkylatlon step 3. Normally liquid material boiling below monoethylbenzene is passed through line I3 and a portion or it is returnedto the dealkylation step through line |4.- The remaining portion passes through line I! joining with line 8 and is supplied .to the alkylation step 2. Ethylene formed in the reaction. due to 5 the dealkylation of polyethylbenzene passes through line It Joining with line 5 and is thus returned to the alkylation step 2. When em-' ploying my preferred dealkylation method using an alumina-containing catalyst and hydrogen separation step 23 whereby the monoethylbenzene produced in dealkylation step 29 may be recovered and the unconverted material may eventually be recycled to the dealkylation step; v

Separation step 23 comprises one or more tractionation steps whereby the products may beseparated as mdlcated. Ethylene may be separated from separator 3| through line 33 joining with line 26 and this is returned to the alkylatipn step 2|. When-hydrogen chloride is used in the dealkylation step, as it is inmy preferred operation, it is recycled through line 34. Makeup hydrogen halide may be added through line 35.

In some cases wherein hydrogen halides are used in alkylation step 2| (as when using certain Friedel-Crafts catalysts) a mixture of ethylene and hydrogen halide may be passed through lines 33 and-28 to alkylation stepfl.

The alkylation step 2| may be carried out using any suitable well-known process, for example,

catalytic processes using catalysis of the Eriedel I Crafts type such as aluminum chloride, zinc chloride and the like, preferably in the presence of hydrogen chloride. Anotherand preferred type] of catalyst is phosphoric acid which has been mixed with a suitable silicious material suchas ,are used. It is an advantage of my process that one may use lower ratios of. benzene to ethylene since'the polyethylbenzenes formed are eventually converted into monoethylbenzene; Ratios of from approximately 1 to about 5 mols of benzene i to l of ethylene'are satisfactory for the alkylation step when using my process.

The dealkylation step '28 maybe. carried out space velocities usually less than about 20 and preferably about 0.2 to about 5 when using a temperature within the range of approximately 450 to about 650 C.

Subatmospheric, atmospheric, or superatmos- I pheric pressures may be employed. Ordinarily temperatures in excess of 100 pounds per square inch are not required. I

- using a silica-alumina, silica-alumina-zirconia.

silica-zirconia, silica alumina-thoria, etc., type of synthetic catalyst composite which is prepared by the separate or simultaneous precipitation of the silica and the added metal oxide.

The preferred operation comprises treating the polyethylbenzenes plussome of the low boilins fractions of benzene and the like with .an alumina or alumina-containing catalyst in the I have presence of an added hydrogen halide. found that this process will selectively remove one or more ethyl groups from polyethylbenzenes such as diethylbenzene, to yield substantial quantities of monoethylbenzene and ethylene.

Since substantial quantities of toluene are also formed in the dealkylation step this may be recovered as a valuable by product.

The amount of liquid hydrocarbons boiling below ethylbenzene which is' recycled may vary.

The use of 1 mol or more of. this fraction per mol of polyethylbenzene processed in the dealkylation step, isjoften helpful in securing increased productiono'f monoethylbenzene and decreased production of less desirable by-products.

When using Friedel-Crafts type catalysts in the alkylation step. a mixture of ethylene and hydrogen halide may be returned directly to the alkylation step.

According to my preferred operation, however, hydrogen halide is separated in a suitable recovery system and may be recycled to the dealkylation step. 7

The dealkylation step of my preferred operation may be carried out using alumina such as the activated alumina of commerce or any other type of alumina except the inactive alpha, beta, or delta forms of anhydrous aluminum oxide. For example, hydrated aluminum oxides may be calcined under controlled conditions to form gamma alumina which is a suitable catalyst. The hydrogen halide is preferably hydrogen chloride but may also under some conditions be of alumina, for example, silica-alumina and the like. Moreover, bauxite or other natural alumina-containing earths may be used, preferably after calcination.

Temperature conditions in the dealkylation step range from approximately coo-700 C. at

This step of the invention requires correlation of temperature, pressure, and space velocity to bring about a maximum conversion of the polyethylbenzene to monoethylbenzene and to minimize destructive side reactions.

The following exampleis given to illustrate my invention but .should not be construed as limitin: it to the exact conditions shown therein.

When operating according to my invention using a solid'phosphoric acid catalyst for the alkylation of benzene with' ethylene, a temperature of about 200 to 400 C. may be used. A temperature-of 275 C. is satisfactory. A 4:1 ratio ofbenzene to ethylene is employed. The pressure may be 900 pounds per square inch. The deallrylation step was carried out using a gamma alumina catalyst prepared by calcining activated alumina obtained 'from'the Aluminum Ore Company at about 5505' C. until no further water was evolved; A mixture of approximately equimolecular quantities of hydrogen chloride and polyethylbenzene was contacted with this catalyst at about5 50 C. and atmospheric pressure. The reaction products were fractionated together with w the reaction products from the alkylation step.

A ratio of about 3 mols of benzene to 1 mol of polyethylbenzene was maintained in the dealkylation step. The ethylene was returned to the alkylation step. A total yield of 95.6 molal per cent of monoethylbenzene based on theethylene I only 80 molal per cent monoethylbenzene based on the ethylene, when using the best operation for alkylation alone. The yield of monoethylbenzene from this combination process is 15 mol per cent more than is obtainable by alkylation alone.

I claim as my invention: 1. A process which comprises subjecting benzene in admixture with ethylene to alkylation,

separating resultant conversion products into a monoethylbenzene fraction and a. polyethylbenzene fraction, subjecting the latter fraction to dealkylation in the presence of a catalyst comprising alumina and hydrogen chloride to form additional monoethylbenzene, benzene and ethylene, and supplying benzene and ethylene thus formed'to the alkylating step.

2. A process which comprises subjecting benzene in admixture with ethylene to alkylation.

separatin resultant conversion products into a monoethylbenzene fraction and a polyethylbenzene fraction, subjecting the latterfraction to dealkylation in the presence of a catalyst com prising alumina and a hydrogen halide to form 

